Adhesives and sealants

Silicone gives the best flexibility and water, UV and temperature resistance, so it's the pick for glazing, sanitary and wet areas — but it can't be painted. Polyurethane gives a strong, paintable, abrasion-resistant elastic bond for movement joints, though it cures slower and should be over-coated for long-term UV exposure. MS-polymer (hybrid) is the all-rounder: paintable, UV-stable, bonds to most substrates including damp, usually without a primer, and is isocyanate-free — which is why it's the go-to for most modern construction bonding and sealing.

As a rule of thumb, MS-polymer hybrids bond well to most common substrates — timber, metal, masonry, glass and many plastics — and tolerate damp surfaces, making them the safest all-round choice. Use neutral-cure silicone for glass and sanitary work, polyurethane for flexible movement joints on concrete and metal, and a construction adhesive for fixing panels, trims and cladding. For load-bearing fixings into concrete, brick or masonry, use a chemical anchoring resin rather than an adhesive. Always bond to clean, sound, dust-free surfaces, and check the product's data sheet for any substrate-specific priming.

Skin time (when the surface skins over and is touch-dry) depends on the chemistry: silicone and MS-polymer typically skin in about 10–30 minutes, while polyurethane is slower at roughly 2–4 hours. Full cure is final strength all the way through. Moisture-curing sealants (silicone and MS-polymer) cure from the outside in at roughly 2–3 mm per 24 hours, so a deeper joint takes proportionally longer — a 6 mm bead can need 2–3 days, and polyurethane can take up to about a week. Warm, humid conditions speed curing; cold or dry conditions slow it. Don't paint, load or disturb a joint until it's cured — always check the product's data sheet for exact figures.

MS-polymer and most polyurethanes can be over-painted (test your paint's adhesion first); standard silicones cannot. For wet areas like bathrooms and kitchens, use a neutral-cure, mould-resistant sanitary silicone or an MS-polymer rated for wet use. For permanently wet or submerged joints, use a product specifically rated for immersion — silicone is the long-standing standard, and MS-polymer may need a primer. For outdoor and UV exposure, silicone and MS-polymer hold up well, while polyurethane performs structurally but should be over-coated for long-term UV to prevent chalking. Check each product page for its specific paintability and exposure ratings.